Method of hot extrusion of metals and alloys on slowly operated presses



Aug. 20, 1968 R. A. KAPRELIAN 3,397,560

METHOD OF HOT EXTRUSION OF METALS AND ALLOYS O N S L 0 W L Y O P E R A T E D P R E s S ES Fig 2 INVENTOR.

ATTOAIVEVS'.

United States Patent 20,803 1 Claim. (CI. 72-41) In hot extrusion of steel and of metals and alloys difficult to deform the die is lubricated by placing against it a disc made of a deformable solid material able to become superficially viscous by contact with the hot billet to be extruded. In this extrusion the disc is either solid or hollowed in its center portion to offer a large surface of contact with the front face of the billet as soon as the latter is in the container.

FIGURE 1 is an axial section view of an example of an extrusion in a known manner, and its upper part shows a billet 1 in a container 1a before the beginning of the extrusion. The billet has a large surface of contact with a deformable disc of agglomerated lubricant 2, which rests against the face 3a of a die 3. The lower part of FIGURE 1 shows the extruding billet wherein the disc 2 has deformed into shape 2' and an extruded bar 4 has been produced.

When using presses with a short lasting operating cycle (for example 30 to 80 seconds), the initial compression of the lubricating disc and of the billet in the container as well as the immediately following extrusion occur within a short time (for example 2 to 5 seconds). Thanks to the short time of contact between the billet and the lubricant, it is possible to select the composition of the lubricating disc so that (i) during the compression the surface of the disc is softened enough but not too much for properly lubricating the beginning of the extrusion operation; and (ii) the bulk of the disc is progressively softened. This produces a continuous thin film of lubricant for the extrusion operation.

One can also use slowly operating presses, i.e., presses with a long cycle of working, for example several minutes and even exceeding minutes. Generally, these presses are very powerful; the contact time between the billet and the lubricant is comparatively long; it reaches or even exceeds 10 to seconds. When using lubricating discs with such presses, the lateral surface of the extruded product shows scars and depressions denoting that an excessive amount of glass has flowed along with the metal during its extrusion.

This invention avoids this drawback and relates to an improvement in the method of lubricating the die in the hot extrusion of metals and alloys from slowly operating presses. More specifically, the method comprises forming a ring of agglomerated lubricating powder having the same outside diameter as the billet and such a volume that after upsetting it becomes substantially trapped between the lateral surface of the container, the entrance face of the die and the previously rounded or chamfered portion of the billet, placing the ring against the entrance face of the die, introducing the billet and proceeding the extrusion.

Before any deformation, the contact between the billet heated to hot extrusion temperature and this ring occurs only along a small surface area.

Just before being upset, the hot billet upsets the ring of the deformable lubricating-material and, at the same time, it melts a small superficial amount of the latter sufiicient for covering the main part of the front billet face "ice with a continuous thin film of viscous lubricant. This film initially ensures a proper lubricating and thermalinsulation between the billet and the entrance face of the die.

When the extrusion is proceeding, the ring of lubricant in a solid state has been trapped between the container wall, the die and the peripheral rounded or chamfered front portion of the billet. While the metal of the billet slowly flows along the small surface of the lubricating ring, a small amount of the ring melts and radially flows in a film along the die face so that the extrusion is properly lubricated.

It is thus possible to use with slowly operating presses the same lubricating material as with fast operating presses, and to achieve at the same time a correct lubrication both at the beginning of and during the extrusion.

The method according to the invention is particularly advantageous when the extrusion ratio is high, because, in this case, the entrance face of the die has a large radial width and the mass of lubricant softened along it in the known manner would soon be detrimental for the quality of the extruded bar.

FIGURE 2 is an axial section view which shows an example of the die lubrication according to the invention, and its upper part shows a billet 1 in the container 1a before the beginning of the extrusion. Substantially only its peripheral, rounded outer front edge is in contact with a part of a deformable ring of agglomerated lubricant 2a, which rests in the angle formed by the die and the container 1a. The lower part of FIGURE 2 shows the extrusion operation wherein the solid ring of lubricant is limited by a circle 5, within which only a film 6 of lubricant flows from its mass 2 between the billet 1 and the die 3.

The method according to the invention is applicable to any die shape which provides a recess for the solid lubricant, whether the entrance die face is uniformly flat, or fiat with a conical junction to the container wall, or slightly conical along its whole width. The down stream shape of the lubricating ring has to be designed to match with the relevant part of the die face.

Example.Carbon steel billets 19%" in diameter were extruded into round solid bars 6%" in diameter. 0n each billet, a 2" radius was machined along the front peripheral edge, then the billet was heated to 2100 F. Next, its lateral surface was coated with a glass lubricant in a known manner and it was inserted into the container of an extrusion press which had a force of 12,000 sh. tons. The inside diameter of the container was 20 /2", and its downstream end was fitted with a flat faced die against which a ring of agglomerated glass powder was placed. The half axial section of the ring was shaped in a square, the sides of which were 2" so that the inside diameter of the ring was 15%. Twenty seconds after the billet was inserted into the container, the whole force of the press was switched on and an extruded product was obtained. The entire length of the product showed a great dimensional accuracy and was free from any surface defect, which proved a thoroughly adequate lubrication.

While I have shown and described a preferred embodiment of my invention, it may be otherwise embodied within the scope of the appended claim.

Iclaim:

1. In hot extrusion of metals and alloys on a slowly operating press, the invention comprises forming a ring of agglomerated lubricating powder having the same outside diameter as the billet and such a volume that after upsetting it becomes substantially trapped between the lateral surface of the container, the entrance face of the 3 die and the previously rounded or chamfered portion of the billet, placing the ring against the entrance face of the die, introducing the billet and proceeding the extrusion.

References Cited 5 UNITED STATES PATENTS 2,887,224 5/1959 St-ulen 72253 2,946,437 7/1960 Edgecombe 72-42 4 Clatot et a1. 72-42 Frost 72-42 Bullet 7241 Stulen 7241 Buffet 72-41 CHARLES W. LANHAM, Primary Examiner.

E. M. COMBS, Assistant Examiner. 

1. IN HOT EXTRUSION OF METALS AND ALLOYS ON A SLOWLY OPERATING PRESS, THE INVENTION COMPRISES FORMING A RING OF AGGLOMERATED LUBRICATING POWDER HAVING THE SAME OUTSIDE DIAMETER AS THE BILLET AND SUCH A VOLUME THAT AFTER UPSETTING IT BECOMES SUBSTANTIALLY TRAPPED BETWEEN THE LATERAL SURFACE OF THE CONTAINER, THE ENTRANCE FACE OF THE DIE AND THE PREVIOUSLY ROUNDED OR CHAMFERED PORTIONOF THE BILLET, PLACING THE RING AGAINST THE ENTRANCE FACE OF THE DIE, INTRODUCING THE BILLET AND PROCEEDING THE EXTRUSION. 